Living Kidney Donor Phenotype and Likelihood of Postdonation Follow-up

Change in Body Mass Index and Attributable Risk of New-Onset Hypertension Among Obese Living Kidney Donors

OBJECTIVE

To examine whether body mass index (BMI) changes modify the association between kidney donation and incident hypertension.

BACKGROUND

Obesity increases hypertension risk in both general and living kidney donor (LKD) populations. Donation-attributable risk in the context of obesity, and whether weight change modifies that risk, is unknown.

METHODS

Nested case-control study among 1558 adult LKDs (1976-2020) with obesity (median follow-up: 3.6 years; interquartile range: 2.0-9.4) and 3783 adults with obesity in the Coronary Artery Risk Development in Young Adults (CARDIA) and Atherosclerosis Risk in Communities (ARIC) studies (9.2 y; interquartile range: 5.3-15.8). Hypertension incidence was compared by donor status using conditional logistic regression, with BMI change investigated for effect modification.

RESULTS

Overall, LKDs and nondonors had similar hypertension incidence [incidence rate ratio (IRR): 1.16, 95% confidence interval (95% CI): 0.94-1.43, P =0.16], even after adjusting for BMI change (IRR: 1.25, 95% CI: 0.99-1.58, P =0.05). Although LKDs and nondonors who lost >5% BMI had comparable hypertension incidence (IRR: 0.78, 95% CI: 0.46-1.34, P =0.36), there was a significant interaction between donor and >5% BMI gain (multiplicative interaction IRR: 1.62, 95% CI: 1.15-2.29, P =0.006; relative excess risk due to interaction: 0.90, 95% CI: 0.24-1.56, P =0.007), such that LKDs who gained weight had higher hypertension incidence than similar nondonors (IRR: 1.83, 95% CI: 1.32-2.53, P <0.001).

CONCLUSIONS

Overall, LKDs and nondonors with obesity had similar hypertension incidence. Weight stability and loss were associated with similar hypertension incidence by donor status. However, LKDs who gained >5% saw increased hypertension incidence versus similar nondonors, providing support for counseling potential LKDs with obesity on weight management postdonation.

Center Variation and Risk Factors for Failure to Complete 6 Month Postdonation Follow-up Among Obese Living Kidney Donors

BACKGROUND

Living kidney donors in the United States who were obese at donation are at increased risk of end-stage renal disease and may benefit from intensive postdonation follow-up. However, they are less likely to have complete follow-up data. Center variation and risk factors for incomplete follow-up are unknown.

METHODS

Adult living kidney donors with obesity (body mass index, ≥30 kg/m) at donation reported to the Scientific Registry of Transplant Recipients from January 2005 to July 2015 were included (n = 13 831). Donor characteristics were compared by recorded serum creatinine at 6 months postdonation, and multilevel logistic regression models were used to estimate odds of 6-month creatinine.

RESULTS

After adjustment, older age, female sex, and donation after implementation of new center follow-up requirements were associated with higher odds of 6-month creatinine, with lower odds for obese donors with a history of smoking, biologically related donors, and at centers with higher total living donor volume. 23% of variation in recorded 6-month serum creatinine among obese donors was attributed to center (intraclass correlation coefficient: 0.232, P < 0.001). The adjusted probability of 6-month creatinine by center ranged from 10% to 91.5%.

CONCLUSIONS

Tremendous variation in recorded 6-month postdonation serum creatinine exists among obese living donors, with high volume centers having the lowest probability of follow-up. Moreover, individual-level characteristics such as age, sex, and relationship to recipient were associated with recorded 6-month creatinine. Given increased risk for end-stage renal disease among obese living donors, center-level efforts targeted specifically at increasing postdonation follow-up among obese donors should be developed and implemented.

Association Between Living Kidney Donor Postdonation Hypertension and Recipient Graft Failure

BACKGROUND

Recipients of kidneys from living donors who subsequently develop end-stage renal disease (ESRD) also have higher graft failure, suggesting the 2 donor kidneys share risk factors that could inform recipient outcomes. Given that donor ESRD is rare, an earlier and more common postdonation outcome could serve as a surrogate to individualize counseling and management for recipients. Hypertension is a frequent event before donor ESRD; thus, early postdonation hypertension might indicate higher risk of graft failure.

METHODS

We studied Scientific Registry of Transplant Recipients data to quantify the association between early postdonation hypertension and recipient graft failure using propensity score-weighted Cox proportional hazards regression. We also examined the association between postdonation systolic blood pressure and graft failure.

RESULTS

Of 37 901 recipients, 2.4% had a donor who developed hypertension within 2 years postdonation. Controlling for donor and recipient characteristics, recipients whose donors developed hypertension had no higher risk for graft failure (adjusted hazard ratio [aHR] 1.03, 95% confidence interval [CI] 0.85-1.25, P = 0.72). This was consistent among subgroups of recipients at higher risk for adverse outcomes due to hyperfiltration: African American recipients (aHR 1.10, 95% CI 0.70-1.73, P = 0.68) and those with ESRD caused by hypertension (aHR 1.10, 95% CI 0.65-1.85, P = 0.73) or diabetes (aHR 0.80, 95% CI 0.56-1.13, P = 0.20). However, graft failure was associated with postdonation systolic blood pressure (per 10 mm Hg, aHR 1.05, 95% CI 1.03-1.08, P < 0.001).

CONCLUSIONS

Although postdonation systolic blood pressure is associated with graft failure, the reported diagnosis of hypertension as determined by the requirement for blood pressure treatment early postdonation did not portend a higher risk of recipient graft failure in the same way as eventual postdonation ESRD.

Early Hypertension and Diabetes After Living Kidney Donation: A National Cohort Study

BACKGROUND

Living kidney donors have an increased risk of end-stage renal disease, with hypertension and diabetes as the predominant causes. In this study, we sought to better understand the timeline when these diseases occur, focusing on the early postdonation period.

METHODS

We studied 41 260 living kidney donors in the United States between 2008 and 2014 from the Scientific Registry of Transplant Recipients and modeled incidence rates and risk factors for hypertension and diabetes.

RESULTS

At 6 months, 1 year, and 2 years postdonation, there were 74, 162, and 310 cases, respectively, of hypertension per 10 000 donors. Donors who were older (per 10 y, adjusted incidence rate ratio [aIRR], 1.40; 95% confidence interval [CI], 1.29-1.51), male (aIRR, 1.31; 95% CI, 1.14-1.50), had higher body mass index (per 5 units, aIRR, 1.29; 95% CI, 1.17-1.43), and were related to their recipient (first-degree relative: aIRR, 1.28; 95% CI, 1.08-1.52; spouse: aIRR, 1.34; 95% CI, 1.08-1.66) were more likely to develop hypertension, whereas donors who were Hispanic/Latino were less likely (aIRR, 0.71; 95% CI, 0.55-0.93). At 6 months, 1 year, and 2 years, there were 2, 6, and 15 cases of diabetes per 10 000 donors. Donors who were older (per 10 y: aIRR, 1.42; 95% CI, 1.11-1.82), had higher body mass index (per 5 units: aIRR, 1.52; 95% CI, 1.04-2.21), and were Hispanic/Latino (aIRR, 2.45; 95% CI, 1.14-5.26) were more likely to develop diabetes.

CONCLUSIONS

In this national study, new-onset diabetes was rare, but 3% of donors developed hypertension within 2 years of nephrectomy. These findings reaffirm that disease pathways for kidney failure differ by donor phenotype and estimate the population most at-risk for later kidney failure.